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A new study led by researchers at the University of Maryland School of Medicine has revealed a notable link between blood type and the risk of early-onset stroke, with individuals possessing blood type A facing the highest risk. The findings, published in the journal Neurology, are based on a meta-analysis of 48 genetic studies, encompassing data from nearly 17,000 people who suffered ischemic strokes before the age of 60 and almost 600,000 stroke-free controls.
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People with blood type A have a 16% higher risk of experiencing an early-onset ischemic stroke (before age 60) compared to those with other blood types.
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In contrast, those with blood type O—the most common blood group globally—show a 12% lower risk of early stroke.
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Blood types B and AB were found to have weaker or mixed associations with early stroke risk.
The researchers believe the increased risk for blood type A may be related to blood-clotting factors. Non-O blood types, especially type A, generally have higher levels of clot-promoting proteins such as von Willebrand factor and Factor VIII, which could predispose them to ischemic events. However, the exact mechanisms remain unclear, and further research is needed to fully understand the biological pathways involved.
Dr. Steven Kittner, a senior author of the study, emphasized that while the statistical association is significant, the absolute increase in risk for individuals with blood type A is modest. “There is no need for extra vigilance or screening in this group,” Kittner stated, adding that most strokes still occur in people over 65, and traditional risk factors like smoking, hypertension, and diabetes remain far more influential.
The study participants were drawn from diverse regions, including North America, Europe, Japan, Pakistan, and Australia, though people of non-European ancestry made up only 35% of the sample. The authors note that further research in more diverse populations is needed to confirm and expand upon these findings.
“We still don’t know why blood type A would confer a higher risk, but it likely has something to do with blood-clotting factors like platelets and cells that line the blood vessels as well as other circulating proteins, all of which play a role in the development of blood clots,” said Dr. Kittner.
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The findings highlighted in this article are based on statistical associations from large population studies and do not imply that blood type alone determines stroke risk. The increase in risk for blood type A is relatively small, and traditional risk factors such as high blood pressure, smoking, diabetes, and lifestyle remain the most important contributors to stroke risk. Individuals should not make health decisions based solely on blood type and are encouraged to consult healthcare professionals for personalized advice.
